Chronic estrogen treatment replaces striatal dopaminergic function in ovariectomized rats

Eight-week-old female Sprague-Dawley rats were divided into three groups: o variectomized rats (OVX); ovariectomized rats treated with estradiol valera te (E2), 20 mug subcutaneously (s.c.) twice weekly for 12 weeks (OVX+E2 gro up); and sham-operated control rats treated with vehicle alone (controls). Spontaneous locomotor activity was measured for 24 h, and then again after the administration of methamphetamine (1 mg/kg, i.p.). In addition, striata l contents of dopamine (DA) and its metabolites were measured. Using an in vivo microdialysis technique, changes in extracellular striatal dopamine co ncentration were studied in a separate set of similarly treated rats after the administration of methamphetamine (0.2 mg/kg, i.p.). Spontaneous locomo tor activity decreased in the OVX group, and estradiol replacement reversed this decreased activity. No significant differences were observed in the c ontents of DA and its metabolites at the striatum among the three groups. T he basal output of DA at the striatum was lower in the OVX group than in th ose of the other two groups. Extracellular DA concentration following metha mphetamine administration was also lower in the rats of OVX group. These re sults indicate that ovariectomy decreases spontaneous locomotor activity, r esponse to methamphetamine. and striatal DA release in the female rats. Chr onic replacement of estrogen reversed spontaneous locomotor activity and DA release by the striatum. These results suggest that chronic administration of estrogen may be beneficial in the treatment of female menopausal patien ts with Parkinson's disease (C) 2001 Published by Elsevier Science B.V.